We propose a 5-year interdisciplinary project to integrate our recent advances and to accelerate research in key areas of virtual patient models for computing radiation doses. The objective is to set the foundation for a paradigm shift in the United States and the rest of the world in the ways that organ doses are calculated for high-energy photon/electron/proton radiotherapy, X-ray/CT imaging, and radiation risk epidemiological studies. We have recently shown that organ dose data obtained using the existing stylized patient models differ remarkably from those from patient-specific anatomies defined by CT, MR and Visible Human images. Therefore, it hypothesized that a new paradigm based on a unified 3-D whole-body computational patient phantom framework, systematically developed from detailed anatomical images and integrated with the modern Monte Carlo simulation tools, can improve the quality of clinical patient care that relies on organ dose calculations. A team of distinguished researchers is assembled to achieve the following Specific Aims: 1) To create a standardized reference library of computational patient 3D/4D anatomical models for both male and female patients of various ages and body sizes. 2) To incorporate these whole-body computational phantoms with easy-to-use Monte Carlo computing tools for 3D/4D radiation transport simulations involving various radiation types for common and emerging therapeutic and diagnostic procedures. 3) To test the hypothesis, we will evaluate the degrees to which the improved anatomical models of patients and modern Monte Carlo simulation tools will impact on the organ dose values and the clinical outcomes. 4) To establish and maintain a national center of computational phantom resources and an internet-based dissemination channel. We develop two common cores in this multi-group effort: 1) A standardized reference library of computational phantoms, and 2) A collection of user-friendly image-processing algorithms and Monte Carlo radiation transport simulation tools. These two cores then support four parallel clinical projects. [unreadable] [unreadable] [unreadable]